Stanford researchers’ soft, growing robot

Medical Innovations

Stanford researchers’ soft, growing robot

A vine-like robot can grow across long distances without moving its whole body.

Edited by Elizabeth Engler Modic

Graduate students Joseph Greer, left, and Laura Blumenschein, right, work with Elliot Hawkes, center, a visiting assistant professor from the University of California, Santa Barbara, on a prototype of the vinebot.

Courtesy of L.A. Cicero

A robot created by mechanical engineers at Stanford University was inspired by natural organisms that cover distance by growing – such as vines, fungi, and nerve cells. A proof of concept of the soft, growing robot passed a series of challenging tests by moving through various obstacles, traveling toward a designated goal, and growing into a free-standing structure. The researchers say this robot could serve a wide range of purposes, particularly in medical devices and search and rescue.

The basic idea behind the robot is a tube of soft material folded inside itself, like an inside-out sock. It grows in one direction when the material at the front of the tube everts, as the tube becomes right-side-out. In the prototypes, the material was a thin, inexpensive plastic, and the robot body everted when the scientists pumped pressurized air into the stationary end. In other versions, fluid could replace pressurized air.

The robot’s design is useful because its tip moves without movement of the body. The group tested the benefits of this method for getting the robot from one place by having it grow through an obstacle course to deliver a sensor. It successfully completed the course even though it was punctured by obstacles. The punctured area didn’t continue to move and self-sealed by staying on top of the object.

Some iterations of these robots included a control system that differentially inflated the body, turning the robot right or left. The researchers developed a software system that based direction decisions on images coming in from a camera at the tip of the robot.

Soft robots can be safer than hard, rigid robots because they are soft and often lightweight. This is especially useful in situations where a robot could be moving in close quarters with a person. Another benefit, in the case of this robot, is that it is flexible and can follow complicated paths.

The vinebot is a tube of soft material that grows in one direction.

Courtesy of L.A. Cicero

Going big and small

Scientists built the prototype by hand and it is powered through pneumatic air pressure. In the future, they would like to create a version that would be manufactured automatically. Future versions may also grow using liquid, and they are also exploring tougher materials such as rip-stop nylon and Kevlar.

The researchers also hope to scale the robot much larger and much smaller to see how it performs. They’ve created a 1.8mm version and believe small growing robots could advance medical procedures. In place of a tube that is pushed through the body, this type of soft robot would grow without dragging along delicate structures.